import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class code3 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        char[] s = in.next().toCharArray();
        int n = s.length;
        int[][] dp = new int[n][n];
        for(int i=n-1;i>=0;i--) {
            for(int j=i;j<n;j++) {
                if(i==j) dp[i][j] = 1;
                if(i<j) {
                    if(s[i]==s[j]) dp[i][j] = dp[i+1][j-1]+2;
                    else dp[i][j] = Math.max(dp[i+1][j],dp[i][j-1]);
                }
            }
        }

        System.out.print(dp[0][n-1]);

    }
}